After years of patient work around the globe, volcanologists and climate modelers are now sure: in the years 536 and 539/40, there occurred at least two volcanic eruptions of almost unprecedented magnitude. The first of them may have been somewhere in the tropics, although the location has not yet been pinned down conclusively. The second was at Lake Ilopango in El Salvador, an explosion so vast that the entire volcano collapsed and left only the flooded caldera that can be seen today, large enough to contain the capital city. It is estimated that Ilopango alone produced up to eighty-seven cubic kilometers of ejecta, a figure big enough to induce double-takes in even the most skeptical authorities.The sulphate emissions may have measured up to two hundred megatonnes, significantly higher than those from Tambora (1815), which was the second-greatest eruption in history. The Ilopango eruption was among the ten largest on earth in the last seven thousand years, and remember, this was preceded by the 536 volcano, so far unlocated. New research suggests these may have been followed by a third major eruption, in 547.
— Neil Price, Children of Ash and Elm: A History of the Vikings
Price goes on to describe the resulting effects upon the people who would become known to history as the Vikings. Global temperatures fell anywhere from two to four degrees Celsius. The catastrophic effects upon Scandinavian agriculture caused up to a fifty percent population loss, and the consequent collapse of social institutions. Various Norse myths can be plausibly read as referring to those terrible times when the sun disappeared for years. I was talking with a geologist friend the other day, and we idly wondered how much of human culture and self-conception has been shaped by natural disasters, from whichever Middle Eastern flood inspired the myth of Noah’s Ark, to Pompeii, to the Lisbon earthquake. If the Big One hit the West Coast tomorrow and sent California to the bottom of the Pacific, how much would that reshape the American identity? If another Ilopango erupted next week, how would the narrative around climate change be altered? It’s kind of funny to think about how much human pride depends upon the benign neglect of volcanoes, earthquakes, and asteroids.